Forging and forming

Pipe and tube manufacturing: what goes wrong and where to inspect

Line pipe, structural tube and pressure tube are produced by forming and welding strip or plate (ERW, LSAW, SSAW) or by piercing and rolling solid billets (seamless).

EN10204 PED2014/68/EU ISO9712

01How the process works

Welded pipe is formed from strip or plate and welded longitudinally or spirally by high frequency induction (ERW) or submerged arc welding (SAW). Seamless pipe is pierced from a heated billet and rolled. Both are sized, straightened, cut, end finished and tested.

The weld seam is the critical feature of welded pipe; dimensional tolerances, hydrostatic test and full length NDT are the main controls. Witnessing hydrotests and reviewing NDT records is a typical third party scope.

Strip, plate or billet. Material verified and identified.
Forming. Roll forming, pressing or piercing.
Welding or rolling. ERW or SAW seam; seamless rolling.
Sizing and finishing. Sizing, straightening, cutting, bevelling.
Testing. Hydrotest, NDT, dimensions, marking.

02What typically goes wrong

Defect	Typical cause	How it is found
Lack of fusion in seam	Welding parameters	UT of weld seam
Hook cracks	Inclusions at strip edge	UT, flattening test
Ovality and thickness deviation	Sizing, piercing	Dimensional gauges, UT
Laminations	Plate quality	UT of body
Hydrotest leaks	Seam defects	Hydrostatic test
Coating holidays	Coating application	Holiday detector

03Where an inspector should look

Before production

Material grade and certificates
Welding and NDT procedures
Test plan per heat and lot

During production

Seam weld parameters
In line UT or ET
Mechanical test sampling

After production

Hydrostatic test witness
Dimensions, ends, marking
Coating and packing for shipment

04Standards and references